An EMG-activated elbow brace for pure motor monoparesis

Pure motor monoparesis (PMM) is an isolated motor deficit, most often following a stroke, that affects a single limb while leaving sensation and other limbs largely unaffected. It's a relatively uncommon presentation — roughly 2.6% of stroke cases — but for the limb it affects, it can mean losing functional strength while retaining full sensation and awareness of the impairment. Most existing upper-body exoskeletons on the patent record are built for rehabilitation programs rather than everyday assistance, leaving a gap for a device meant for daily use.

Requirements were built out using a standard design-controls framework, translating each user need into a measurable design output.

The brace secures aluminum bars to the arm with Velcro, hinged at the elbow joint, with a gear-and-pulley system connecting that hinge to a motor mounted on a harness. EMG electrodes on the bicep feed into an instrumentation amplifier and low-pass filter, buffered through an Arduino Nano, which drives the motor whenever it detects a signal consistent with an intent to flex the elbow.

The device was tested on two users, with the servo successfully activating on bicep flexion and returning to rest position when the muscle relaxed. The securement and signal-reading setup adjusted easily between the two testers without any hardware changes, a good early sign for fitting a wider range of users.